THE ROLE OF BETA-CAROTENE METABOLISM IN LUTEAL FUNCTION

Dairy cattle, which produce milk for human consumption, have major problems with infertility. Successful pregnancies in these animals are essential for milk production and for generating replacement heifers for dairy herds. Infertility in dairy cattle, much of which is due to early pregnancy loss, causes substantial financial losses for producers each year and decreases the sustainability and efficiency of milk production. A common cause of early pregnancy loss is failure of the embryo's signal to prevent regression of the corpus luteum (CL). The CL is a transient endocrine gland that forms on the ovary and produces progesterone, the hormone that maintains pregnancy in all mammals. The yellow color of the CL originates from beta-carotene, a vitamin A precursor, found in the CL. The active form of vitamin A, retinoic acid, has been implicated in regulation of progesterone production and immune function in other organs. Concentrations of beta-carotene in the bovine CL are higher than in any other organ in which it has been measured and progesterone production and immune regulation are key to luteal function, yet little is known about the the role of beta-carotene and retinoic acid in the CL. The goal of this research is to determine whether metabolism of luteal beta-carotene regulates luteal function. The first set of experiments will determine the role of luteal beta-carotene metabolism in regulating luteal progesterone production. The second set of experiments will determine the the role of luteal beta-carotene metabolism in regulating function of luteal immune cells. The third set of experiments will determine the whether estrous cycle stage or pregnancy affect luteal beta-carotene metabolism and retinoic acid signaling. Together, these experiments will determine the role of beta-carotene in regulating luteal function and could lead to applications to which could improve fertility in dairy cattle and even humans.